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PubMed1987

Comparison of high-performance ion-exchange and ion-pair liquid chromatographic methods for the separation of tumour cell nucleotides.

Ion-exchange liquid chromatography (IELC) on a novel anion-exchanger, Polyanion SI HR 5/5, and the ion-pair technique (IPLC) using Hypersil ODS and/or MinoRPC reversed phases with tetrabutylammonium phosphate as pairing agent were compared for the separation of nucleotides. Modifications to the concentration gradient in IELC in the range 0.01-0.3 M ammonium phosphate resulted in the simultaneous separation of twelve to fourteen biologically important nucleotides. IPLC studies revealed that the capacity factors and resolution of nucleotides were more sensitive to the ionic strength than the methanol content. It was concluded that a well controlled ion concentration (0.08-0.09 M sodium chloride) should be maintained in the mobile phase and a linear methanol gradient ranging from 0 to 20% (v/v) was suitable for optimal resolution. Separations of four nucleotides and twelve nucleotides were further improved using a mixed-type reversed-phase column (C2/C18, MinoRPC). Using these complementary methods, it was possible to reveal the metabolic changes induced by different drug treatments (cyclophosphamide, DL-alpha-difluoromethylornithine) in the nucleotide pool of P388 leukaemia cells.

Animals↗
PubMed1975

Adsorption and selection of rhizobia with ion-exchange papers.

Ion exchange papers were used to study the adsorption of 32P-labelled rhizobia on defined surfaces. Two strains of Rhizobium japonicum and one each of R. leguminosarum and R. lupini were compared with Escherichia coli and Bacillus subtilis. The ratio of adsorption to strong and to weak acid papers/strong and weak basic papers was consistantly higher for all rhizobial strains compared to the other bacteria. The process of desorption by increasing the ion-concentration causes about 35% desorption between 0.02 and 0.1 M MgCl2, however, an increase to 1 M does not desorb more labelled Rhizobium japonicum or E. coli cells. The ratio of adsorbed cpm to colony formers, desorbed by 0.1 M NaCl was similar with Rhizobium japonicum for all six ion exchange papers. For E. coli this ratio varied widely for the different papers. The selection of Rhizobium against a more closely related bacterium by this adsorption/desorption procedure was demonstrated with mixed cultures of Rhizobium japonicum and Chromobacterium violaceum giving a more than 80 fold enrichment of the former. Rhizobium japonicum cells, ad/desorbed from all ion exchange papers kept their infectivity and formed nodules on Glycine max with an activity of 20-40 nM C2H4-hr(-1)-mg nodule(-1). A desorption of Rhizobium japonicum from soybean roots also occurred by increasing the ion concentration. 2-3 times as many cells were removed in this way compared to washing with water.

Adsorption↗
PubMed2004

Chromium (III) recovery from waste acid solution by ion exchange processing using Amberlite IR-120 resin: batch and continuous ion exchange modelling.

The use of ion exchange technology was studied to remove chromium (III) from acidic waste solution by Amberlite IR-120 resin. Batch and column experimental tests were conducted to provide data for theoretical models and verify the system performance of the adsorption process. Results of batch equilibrium tests indicated that Langmuir isotherm describes well the adsorption process, whereas experimental data also provide evidence that, under the present experimental conditions, chromium (III) adsorption by Amberlite IR-120 resin is film-diffusion controlled; on the other hand, the theoretical model used in the present investigation was found to predict reasonably well the ion exchange breakthrough performance.

Adsorption↗
PubMed2001

Analysis of fountain solutions for anionic components, including alkylbenzenesulfonates, carboxylates and polyphosphates, by a combination of ion-exchange and ion-exclusion chromatography and inductively coupled plasma atomic emission spectrometry.

A method for the quantitative determination of the major anionic constituents of fountain solutions, typically mono-, di- and hydroxycarboxylates, alkylbenzenesulfonates, and inorganic anions, including orthophosphate and polyphosphates, is presented here for the first time. The analytical problems arising from extensive co-elution of many of these analytes on an ion-exchange column have been resolved through a combination of (i) careful selection of the concentration gradient of the sodium hydroxide eluent; (ii) parallel analysis by ion-exclusion chromatography; and (iii) determination of total phosphorus by inductively coupled plasma atomic emission spectrometry.

Anions↗
PubMed2007

Tailoring elution of tetraalkylammonium ions. Ideal electrostatic selectivity elution order on a polymeric ion exchanger.

Although ion exchange is often depicted as a process driven by electrostatic forces, ionic solvation or hydrophobic forces contribute greatly to ion exchange selectivity and is often the dominant factor. On a variety of commercial anion exchange columns, monovalent ClO4- elutes after doubly charged SO42- and even triply charged PO43-. For identically charged alkali metal ions, electrostatic charge densities based on crystal radii would suggest Li+ to be the most strongly retained on a cation exchanger. In practice, it is typically the least strongly held cation on most cation exchangers, because of its very high hydration energy and with most eluents its capacity factor approaches zero. Even when the ion is very poorly solvated, as with tetraalkylammonium (NR4+) cations, there has never been a report on a polymeric ion exchanger of an ideal electrostatic selectivity order where NR4+ cations elute in their increasing charge density order: R = n-butyl first, followed by n-propyl, ethyl, and last, methyl. We show that this selectivity order is easily achieved on recently described methracrylate-based monolithic capillary cation exchange columns (Ueki, Y.; Umemura, T.; Li, J. X.; Odake, T; Tsunoda, K. Anal. Chem. 2004, 76, 7007-7012) with minor amounts of hydroorganic modifiers. Indeed, under such conditions, Li+ (and other alkali cations) elutes after NMe4+.

Journal Article↗
PubMed2004

Effects of inorganic substances on water splitting in ion-exchange membranes; I. Electrochemical characteristics of ion-exchange membranes coated with iron hydroxide/oxide and silica sol.

The effects of inorganic substances on water splitting in ion-exchange membranes (IEMs) were investigated. In this study, iron hydroxide/ oxide and silica sol were immobilized on the surface of the IEMs. The water-splitting capabilities of the metal-embedded cation-exchange membranes were 10(4)-10(5) times greater than those of the virgin membranes at the same current density. Similarly, silica sol (i.e., triple bond Si-OH groups) deposited on the anion-exchange membrane surface also drastically increased the proton transport numbers. It was thought that the bipolar structure consisting of H- and OH-affinity groups immobilized on the IEM surface increased water-splitting due to the enhancement of water polarization with the help of strong electric fields. This study revealed that metal oxides or silica groups (triple bond Si-OH), as well as metal hydroxides, can be used as catalysts for water splitting.

Journal Article↗
PubMed2004

Overcoming the problem of non-ideal liquid ion exchanger selectivity in microelectrode ion flux measurements.

Ion-selective microelectrodes are a powerful tool in studies on various aspects of cell membrane biology in both animal and plant tissues. Further application of this technique is, however, limited to a large extent by the problem of non-ideal selectivity of the liquid ion exchanger used in the preparation of microelectrodes for ion flux measurements. Because of this problem, which is persistent in many commercial liquid ion exchangers, the microelectrode does not discriminate between the ion of interest and other interfering ions (for example, Mg2+ and Ca2+; Na+ and K+), thereby leading to inaccurate concentration readings and, consequently, inaccurate flux calculations. In this work we show that the existing analytical procedure to overcome this problem, using the inverted Nicolsky-Eisenman equation, is inadequate, and suggest an alternative analytical procedure that can be applied directly to the data obtained with commercially available liquid ion exchangers. We show that this alternative procedure allows accurate measurement of ionic concentrations with non-ideal ion-selective microelectrodes in the presence of interfering ions, and illustrate the method by direct experiment using Ca2+ and Mg2+ as a "case study". Several more examples are given, further illustrating practical applications of the method for study of plant responses to salinity, osmotic and reactive oxygen species stresses.

Algorithms↗
PubMed2000

Optimization of ion-exchange displacement separations. II. Comparison of displacement separations on various ion-exchange resins.

A variety of stationary-phase materials are currently available for the chromatographic purification of biomolecules. However, the effect of various resin characteristics on the performance of displacement chromatography has not been studied in depth. In Part I, a novel iterative scheme was presented for the rapid optimization of displacement separations in ion-exchange systems. In this article, the optimization scheme is employed to identify the optimum operating conditions for displacement separations on various ion-exchange resin materials. In addition, the effect of different classes of separation problems (e.g., diverging, converging or parallel affinity lines) on the performance of displacement separations is also presented. The solid film linear driving force model is employed in concert with the Steric Mass Action isotherm to describe the chromatographic behavior in these systems. The results presented in this article provide insight into the effects of resin capacity and efficiency as well as the type of separation problem on the performance of various ion-exchange displacement systems.

Algorithms↗
PubMed2004

Selective removal of the heavy metal ions from waters and industrial wastewaters by ion-exchange method.

By ion exchange undesirable ions are replaced by others which don't contribute to contamination of the environment. The method is technologically simple and enables efficient removal of even traces of impurities from solutions. Examples of selective removal of heavy metal ions by ion-exchange are presented. They include removal of Pb(II), Hg(II), Cd(II), Ni(II), V(IV,V), Cr(III,VI), Cu(II) and Zn(II) from water and industrial wastewaters by means various modern types of ion exchangers.

Industry↗
PubMed1991

Ion-exchange high-performance liquid chromatography of nucleotides and polypeptides on new types of ion-exchange sorbents, based on polystyrene-coated silicas.

A novel type of ion exchanger was prepared by multipoint covalent binding of polystyrene chains onto the surface of porous silica followed by polymer-analogous modification of the bonded layer. Both anion and cation exchangers were synthesized and examined in the separation of nucleotides and proteins. Rapid and efficient separation of basic polypeptides on strong anion exchangers and that of acidic polypeptides on strong cation exchangers could be achieved. For the separation of complete mixtures of polypeptides the application of zwitter-ionic ion exchangers can be recommended.

Animals↗